1. Field of the Invention
The present invention relates to a technology for monitoring a data recovery available time in a storage system that performs Asynchronous Remote Copy among a plurality of storage devices.
2. Related Art
An importance of nondisruptive business operation and data protection in a business information system is increasing more and more lately due to globalization of a market and due to provision of services 24 hours a day and 365 days a year through Web. However, there exists a lot of risks such as terrorism and natural disasters that possibly lead to disruption and data loss of the business information system.
One of technologies that relieves these risks is Asynchronous Remote Copy in a storage system. The Remote Copy here is a technology of duplicating data by copying data in a certain volume in a storage device to a volume of another storage device.
There are two main types of Remote Copy. One is Synchronous Remote Copy (RCS: Remote Copy Synchronous) of copying the data in real-time as extension of writing in a host and of the other is Asynchronous Remote Copy of copying the data through processing different from the writing in the host. In the case of the Asynchronous Remote Copy, there are also two methods of storing changed data history in a memory (RCA: Remote Copy Asynchronous) and of storing in the memory in combination with a volume (RCD: Remote Copy asynchronous with Disk). The present invention intends the Asynchronous Remote Copy (the both RCA and RCD).
Note that it is said to be preferable to adopt the Asynchronous Remote Copy if a distance between a primary site (a site normally performing business operations) and a remote site (a different site for supporting the business continuity) is distant, e.g., 100 km or more, even though the Synchronous Remote Copy may be adopted naturally if the distance is close, e.g., less than 100 km, in general for convenience of communication performance and the like. That is, assuming a natural disaster such as a huge earthquake beside a terrorism, it is necessary to largely keep the distance between the primary and remote sites and in that case, it is desirable to adopt the Asynchronous Remote Copy.
That is, the use of the Asynchronous Remote Copy allows the remote site to support the business continuity when the primary site is hit by the terrorism, natural disaster or the like even if the distance between the primary and remote sites is distant. To that end, storage devices are provided on the both primary and remote sites in the Asynchronous Remote Copy to deal with the terrorism, natural disaster or the like that is unpredictable when it occurs. Upon that, the Asynchronous Remote Copy realizes the business continuity while minimizing data loss when the primary site is damaged by conforming contents of data stored in the primary and the remote sites as much as possible.
For instance, there has been a practical technology of duplicating contents of a physical volume or logical volume by using the Asynchronous Remote Copy between the storage devices provided in the primary and remote sites and of continuing business operations by using the storage device of the remote site when the primary site is damaged.
When the Asynchronous Remote Copy is carried out, there is a time lag in writing data respectively into the storage devices of the primary and remote sites. Therefore, it is necessary to monitor that data stored in the storage device of the remote site corresponds to data of which point of time in the primary site to be ready for a case when a failure occurs in the primary site. Here, time when the latest data stored in the storage device of the remote site had been written into the storage device of the primary site will be called as data recovery available time with reference to certain time. The lag of time of the data stored in the storage device of the primary site and the storage device of the remote site will be called as a data loss time period.
For instance, assuming that write data issued at 21:00:00 is written into the storage device of the primary site, and assuming that the write data issued at 20:59:20 is written into the storage device of the remote site and no write data is written after that, the data recovery available time is 20:59:20 and the data loss time period is 40 seconds.
US2002/0103980A discloses a technology of monitoring the data recovery available time by utilizing a time stamp (temporal information) embedded by a host into a write I/O (Input/Output) (write request) in a main frame environment.
US2006/0277384A discloses a technology of monitoring the data recovery available time in a SAN (Storage Area Network) environment.
However, US2002/0103980A presupposes a main frame technology in which the temporal information may be given to the write I/O. However, no temporal information is given to the write I/O in Fibre Channel Protocol used in the SAN environment, so that it is difficult to apply the technology of US2002/0103980A to environments other than the main frame.
US2006/0277384A discloses a technology of indicating the data loss time period that is a time lag in writing data respectively into the storage devices of the primary and remote sites. However, US2006/0277384A discloses no technology of indicating the data recovery available time nor discloses accuracy in monitoring the data loss time period.
In view of the problems described above, the invention seeks to provide a technology that is applicable to technologies other than the main frame technology and that monitors the data recovery available time while suppressing a monitoring error within a certain range in a storage system that performs the Asynchronous Remote Copy among a plurality of storage devices.